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Basics

History of PV

How PV Works

Solar Cell Basics

PV Module Basics

Glossary

PV Essentials: 340 Key Technical Terms in English and Chinese (Worth Bookmarking)

Materials

Materials Basics

2026 Failure Ranking of Eight PV Module BOM Materials: What Is Holding Reliability Back?

One Circuit to Understand a Solar Cell: The Single-Diode Model

Solar Cells

PERC

TOPCon

HJT

BC

After 28.29%: How Much Room Is Left in the BC Cell Efficiency Race?

Perovskite & Tandem

PV Glass

Encapsulant Films

Only 3%–4% of the Cost, Yet the Safety Net for 25 Years: What Does PV Encapsulant Actually Do?

"China-Made Pellets" for POE Encapsulants: After Going from Zero to One, How Far Has Localisation Come?

Still Mixing Up EVA, POE and EPE? A Complete Guide to the PV Encapsulant Family

Same Resin, Very Different Films: Inside the Resin and Additive Formulation of PV Encapsulants

A Short Process Where Consistency Is Everything: How a Roll of PV Encapsulant Is Made

Is a "Passing" Degree of Cure Really Enough? Key PV Encapsulant Indicators and Test Methods

Why Does the Same Roll of Encapsulant Behave Differently on Two Lines? Encapsulant and the Lamination Process

From PERC to TOPCon, HJT and BC: Every New Cell Technology Sets Encapsulant a New Exam

With Modules Below RMB 0.7/W, How Should the Encapsulant Cost-and-Efficiency Sums Be Done?

Yellowing, Delamination, Snail Trails, Acetic Acid Corrosion and PID: A Complete Guide to Encapsulant-Related Module Failures

DH, TC, HF, UV, PID: What Do Module Reliability Tests Really Ask of the Encapsulant?

How Many Gates Does a New Encapsulant Have to Pass? Encapsulant Selection, Qualification and Incoming Inspection from the Buyer's View

One Company Holds Half the Market While the Rest Shake Out Through Losses: The PV Encapsulant Industry Landscape

To Crosslink or Not? How Perovskites, Flexible Modules and Recycling Are Rewriting the Future of PV Encapsulants

Backsheets

Ribbons

Copper-Clad Aluminum (CCA) Ribbon: The Cost Is Tempting, So Why Are Leading PV Makers Still Holding Back?

The Workhorse Alloy of Low-Temperature Ribbon: Sn32Pb42Bi26 in PV Ribbon Today and Tomorrow

Copper Tops 110,000 CNY/t: How Far Is Copper-Clad Aluminium Ribbon from Mass Production?

After 0.16 mm: How Much Thinner Can 0BB Round Ribbon Go?

Ribbon: The Most Overlooked "Blood Vessel" in a PV Module

From Flat Ribbon to Round Wire: PV Ribbon Structure and Classification Explained

Ribbon Materials: The Fine Points of Copper Substrate and Coating

How a Spool of Ribbon Is Made: The PV Ribbon Production Process

Is the Ribbon Good? PV Ribbon Test Methods and Key Indicators

Bonding Ribbon to Cell: A Complete Guide to PV Module Soldering

Common Ribbon-Related Failures: From Dark EL Cells to Cracked Solder Joints

Ribbon and Module Reliability: What Are Reliability Tests Really Testing in the Ribbon?

The PV Ribbon Industry Today and Tomorrow: Growing Volumes, Thinning Margins, Diverging Technologies

Soldering Flux

Frames

What a PV Module Frame Actually Does: The Module's Skeleton

Frame Materials: Why 6063 Aluminum Alloy?

Steel Module Frames: How Far Has Mass Production Got?

Composite Frames Offshore: The Real Test Is Not Salt Mist, but a Slowly Opening Slot

Silicones

Junction Boxes

What a Junction Box Does: Functions and Roles

Why Is Junction Box Creepage Distance Getting Harder in the 1500 V Era?

Bypass Diodes

The Lifesaver in the Junction Box: PV Bypass Diodes Explained

Connectors

How a Small MC4 Connector Has Stayed on Top in PV for Twenty Years

MC4 vs. MC4-Evo 2: What Is Actually Different?

It Plugs In, But Does It Mate? How Micron-Scale Slip in Cross-Mated PV Connectors Grinds Its Way to a Fire

UV Adhesives

The Hidden Protagonist in 0BB and BC Modules: A Guide to the Four Families of PV UV Adhesives

One Drop of Glue, One Ring of Soft Encapsulant: How 0BB Dispensing Adhesives Poison POE/EVA Crosslinking

Other Materials

Swapping Glass for a Film: How ETFE Makes PV Modules Flexible

Modules

Module Basics

From 182+X to 2382×1134: Why Did Module Sizes End Up Converging "by Tacit Agreement"?

Layout & Circuit Design

Structure & Mechanical Load

Bifacial & Glass-Glass

BOM & Cost Reduction

Process

Stringing

Layup

Lamination

Framing & J-Box Mounting

EL & IV Testing

Reliability & Failures

Testing Basics

55 PV Plants Surveyed: Is One in Five Modules Cracked? How to Read the Numbers

Every Material Passed, Yet the Module Died in Damp Heat: What Lies Between IEC 62788 and IEC 61215?

The Desert's Hidden Killer: How Much Yield Do AR Coatings Worn Off by Sand Really Cost?

Offshore PV Goes Mainstream: Salt Mist, Sealing and Wave Splash, Three Trials Every Module Must Survive

Failure Basics

One Drop of Glue, One Ring of Soft Encapsulant: How 0BB Dispensing Adhesives Poison POE/EVA Crosslinking

MQT 01 Visual Inspection

MQT 02 Maximum Power Determination

MQT 03 Insulation Test

MQT 04 Temperature Coefficients

MQT 06 Performance at STC

MQT 07 Performance at Low Irradiance

MQT 08 Outdoor Exposure

MQT 09 Hot-Spot Endurance

The Hot-Spot Effect in PV Modules, Step by Step: How a Shaded Cell Gets Driven Down to −16.8 V

5 % or 1 %? In Hot-Spot Testing, the Real Problem Is a Worst Case That Moves

MQT 10 UV Preconditioning

MQT 11 Thermal Cycling (TC)

The TC200 Thermal Cycling Test for PV Modules: Test Conditions, Failure Signatures and Failure Mechanisms

MQT 12 Humidity Freeze (HF)

MQT 13 Damp Heat (DH)

DH1000 Damp Heat Testing of PV Modules: Test Conditions, Failure Signatures and Failure Mechanisms (TOPCon as an Example)

MQT 14 Robustness of Terminations

MQT 15 Wet Leakage Current

MQT 16 Static Mechanical Load

MQT 17 Hail Test

MQT 18 Bypass Diode Testing

MQT 18.1 Bypass Diode Thermal Test (Junction Temperature)

MQT 18.2 Bypass Diode Functionality Test

MQT 19 Stabilization

MQT 20 Cyclic (Dynamic) Mechanical Load

MQT 21 Potential-Induced Degradation (PID)

PV PID Series #1: High Voltage Difference, the Entry Ticket to PID

PV PID Series #2: PID-s, PID-p and PID-c, the Root Causes of Three Kinds of PID

PV PID Series #3: Temperature, Humidity, Glass and Encapsulant, the Other Half of What Decides PID

PV PID Series #4: How Is PID Tested, and How Should You Read a Test Report?

PV PID Series #5 (Finale): Suspected PID in a Plant - How to Investigate, Recover and Prevent It

MQT 22 Bending Test

Tests from Other Standards

Thermal Runaway (IEC 62979)

Is 1.25 × Isc Enough? Calculating the Thermal-Runaway Boundary of Bypass Diodes in High-Gain Bifacial Applications

LID

LeTID

UVID

How Much of the Power Lost in UV Testing Is Real? Trina Splits TOPCon UVID into Reversible and Irreversible

Same UV Test, Very Different UVID Results: Why? A New Fraunhofer Paper Explains

How UV Light "Steals" Module Lifetime: UVID Explained

Microcracks

Snail Trails

Backsheet Cracking & Yellowing

Junction Box Failures

Delamination

Standards

Standards Basics

How Much of the Power Lost in UV Testing Is Real? Trina Splits TOPCon UVID into Reversible and Irreversible

What Every PV Professional Should Know: How Do IEC 61215 and IEC 61730 Differ?

IEC, UL, GB, Industry and Association Standards: How PV Standards Relate

Is Passing IEC 61215 Enough? A Guide to the "Extra Exams" for PV Module Reliability

If the Module Already Passed IEC 61730, Why Do Junction Boxes and Backsheets Need Their Own Certification?

IEC 61215

IEC 61730

IEC TS 62915

Changed a Material: Does the Certificate Still Count? A Guide to the IEC TS 62915 Retesting Specification

A Second-Source Material Means Retesting Everything? Using IEC TS 62915 to Keep a Whole Product Family Certified with Minimal Samples

Certification in Practice

Frontiers

AI for PV

AI Is Here: Will PV Technical Jobs Be Replaced?

Five of the Most Useful AI Prompts for PV Engineers

Read the IEC 61215 Test Sequence in Ten Minutes with AI

Build a "Self-Learning" EL Defect Detection AI on Your Own Computer

Perovskite Literature AI Assistants Are Only "Half Right": The Real Weakness Is Not the Model but the Data Table

Space PV

Nearly CNY 100 Million on "Roll-Up Solar Wings": Space PV Through the Eyes of a PV Engineer

Perovskite & Tandem

The New York Times Says Tandem Cells Could Help the US Catch China in Solar. We Doubt It

A 1.95 eV Perovskite Hits 16.5% Certified — How Should We Read “Passing IEC 61215 at the Cell Level”?

35% in the Lab, but Does the Math Work Outdoors? Unpacking Current Mismatch in Perovskite/Silicon Tandems

Zero-Busbar (0BB)

Shingled Modules

Lightweight & Flexible PV

Modules Without Glass: Unpacking the KPIs of the EU's SUNRISE Project

BIPV

Vehicle-Integrated PV

Module Recycling

Can Thermoplastic Encapsulants Rescue Recyclability? The Standards Tug-of-War between Creep Resistance and Dismantling

The First PV Modules Are Retiring. What Happens Next?

Insights

Weekly Reports

Monthly Reports

News & Views

Can Thermoplastic Encapsulants Rescue Recyclability? The Standards Tug-of-War between Creep Resistance and Dismantling

Stop Calling Appliance Makers "Outsiders" in Solar

Musk Raises 200 GW Again with Jensen Huang: How Long Will This Solar Story Run?

Offshore PV Corrosion Protection Gets an Industry Standard: The Text Isn't Out Yet, but Your BOM Should Be Ready

Perovskite Modules Head to Orbit Again: What's Different About GCL Optoelectronics' In-Orbit Test?

Payrolls Up Just 29,000, Rate-Hike Bets Cool: Can PV Breathe Easier?

Will China's PV Market Improve by Year-End? Our View: The Fall Has Stopped, but Recovery Is Still Far Off

First Price Rise in October: Three Module Makers Raise Prices — Is the Slide Over?

DiCaprio's Third Bet on Solar Still Isn't on Modules

US Tandem Modules Are \"Coming Soon\", China's GW Lines Are Ramping: The Real Gate Is the Bank

5–10× Faster Inspection, 0.1% Missed Defects: How to Read the Six Numbers as AI Enters LONGi's Storage Line

Nameplate 0.70, Field 0.60: How Much Is the Bifacial Rear-Side Gain Overstated?

584 GW: BNEF Cuts Its Global Solar Outlook Again. What Does China's −29% Mean?

An Efficiency Ranking Unchanged for Four Months: BC Tops Out at 25%, TOPCon Close Behind, HJT Holds 740 W

Eight Makers Cut Prices and High-Efficiency Modules Slip Too: How Far Are Module Prices from the \"Hangzhou Floor\"?

China's New Module Standard Is Not Yet in Force, but 23.2% Is Already in Tenders: The Countdown for Older Lines Has Moved Forward

Same UV Test, Very Different UVID Results: Why? A New Fraunhofer Paper Explains

China's Wind and Solar Pass 2 TW: The Next Phase of PV Is About Reliability

Buyer's View

Price Trends

Series

PID Series

Junction Box Series

Ribbon Series

Flux Series

Encapsulant Series

PV Glass Series

Frame Series

On this page

Home / Reliability & Failures

Backsheet Cracking & Yellowing

Level: IntermediatePlanned

Backsheet failure symptoms and material root causes

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