Mechanical residual stresses within multilayer thin-film device stacks become problematic during thermal changes because of differing thermal expansion and contraction of the various layers. Thin-film photovoltaic (PV) devices are a prime example where this is a concern during temperature fluctuations that occur over long deployment lifetimes. Here, we show control of the residual stress within halide perovskite thin-film device stacks by the use of an alkyl-ammonium additive. This additive approach reduces the residual stress and strain to near-zero at room temperature and prevents cracking and delamination during intense and rapid thermal cycling. We demonstrate this concept in both n-i-p (regular) and p-i-n (inverted) unencapsulated perovskite solar cells and minimodules with both types of solar cells retaining over 80% of their initial power conversion efficiency (PCE) after 2500 thermal cycles in the temperature range of −40 to 85 °C. The mechanism by which stress engineering mitigates thermal cycling fatigue in these perovskite PVs is discussed.

中文翻译：

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减轻钙钛矿光伏热循环疲劳的应力工程

由于各层的热膨胀和收缩不同，多层薄膜器件堆叠内的机械残余应力在热变化期间成为问题。薄膜光伏 (PV) 设备就是一个典型的例子，在较长的部署寿命期间出现温度波动时，这是一个值得关注的问题。在这里，我们展示了通过使用烷基铵添加剂来控制卤化物钙钛矿薄膜器件堆叠内的残余应力。这种增材方法在室温下将残余应力和应变降低到接近于零，并防止在剧烈和快速的热循环过程中出现裂纹和分层。我们在 nip（常规）和 pin（倒置）未封装钙钛矿太阳能电池和微型模块中展示了这一概念，两种类型的太阳能电池在 2500 次热循环后，在 - 40 至 85°C。讨论了应力工程减轻这些钙钛矿光伏器件热循环疲劳的机制。