Annealing-free fluoropolymer protective layer for mitigating snail trails in crystalline silicon photovoltaic modules

Abstract

Snail trail faults, caused by the reaction between the silver electrodes of crystalline silicon (c-Si) photovoltaic (PV) cells and various chemicals, lead to electrode disconnection, performance degradation, and localized heating. This study aimed to develop stable c-Si PV modules by applying two different room-temperature processed protective layers: cyclic transparent optical polymer (CYTOP) and perhydropolysilazane (PHPS). Both coatings are designed to prevent acid-induced reactions at the cell's electrodes. After 3 min of direct exposure to nitric acid, c-Si PV cells with protective coatings retained 75 % of their electrode height and performance, while 66 % of electrodes without protective layers were corroded. As a result, the series resistance of uncoated c-Si PV cells increased more than tenfold, whereas cells with PHPS and CYTOP coatings exhibited only a twofold increase. A 1000-h damp heat test of the encapsulated c-Si PV cells revealed that CYTOP effectively suppressed electrode degradation and preserved its shape, outperforming encapsulated uncoated cells. While the PHPS film demonstrated excellent protective properties at the cell level, its performance at the module level was hindered by poor adhesion between the encapsulant and the cell, leading to delamination. Therefore, a thin layer of CYTOP shows strong potential for protecting c-Si PV modules from acid-related degradation during operation. This work offers valuable insights for designing more reliable PV modules.