Jacobs Daniel A, Wu Yiliang, Shen Heping, Barugkin Chog, Beck Fiona J, White Thomas P, Weber Klaus, Catchpole Kylie R
Centre for Sustainable Energy Systems, Research School of Engineering, The Australian National University, Canberra, Australian Capital Territory, Australia.
Phys Chem Chem Phys. 2017 Jan 25;19(4):3094-3103. doi: 10.1039/c6cp06989d.
The issue of hysteresis in perovskite solar cells has now been convincingly linked to the presence of mobile ions within the perovskite layer. Here we test the limits of the ionic theory by attempting to account for a number of exotic characterization results using a detailed numerical device model that incorporates ionic charge accumulation at the perovskite interfaces. Our experimental observations include a temporary enhancement in open-circuit voltage following prolonged periods of negative bias, dramatically S-shaped current-voltage sweeps, decreased current extraction following positive biasing or "inverted hysteresis", and non-monotonic transient behaviours in the dark and the light. Each one of these phenomena can be reproduced and ultimately explained by our models, providing further evidence for the ionic theory of hysteresis as well as valuable physical insight into the factors that coincide to bring these phenomena about. In particular we find that both interfacial recombination and carrier injection from the selective contacts are heavily affected by ionic accumulation, and are essential to explaining the non-monotonic voltage transients and S-shaped J-V curves. Inverted hysteresis is attributed to the occurrence of "positive" ionic accumulation, which may also be responsible for enhancing the stabilized open-circuit voltage in some perovskite cells.
钙钛矿太阳能电池中的滞后现象如今已确凿地与钙钛矿层中移动离子的存在联系起来。在此，我们通过尝试使用一个详细的数值器件模型来解释一些奇特的表征结果，以此来检验离子理论的局限性，该模型纳入了钙钛矿界面处的离子电荷积累。我们的实验观察结果包括：长时间施加负偏压后开路电压的暂时增强、显著的S形电流-电压扫描、正偏压后电流提取的降低或“反向滞后”，以及在黑暗和光照条件下的非单调瞬态行为。这些现象中的每一种都可以由我们的模型重现并最终得到解释，这为滞后现象的离子理论提供了进一步的证据，同时也为导致这些现象的相关因素提供了有价值的物理见解。特别是我们发现，界面复合和来自选择性接触的载流子注入都受到离子积累的严重影响，并且对于解释非单调电压瞬态和S形J-V曲线至关重要。反向滞后归因于“正”离子积累的发生，这也可能是一些钙钛矿电池中稳定开路电压增强的原因。
