State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, P.R. China.
Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, P.R. China.
Sci Rep. 2017 Apr 12;7:46141. doi: 10.1038/srep46141.
To obtain high performance CHNHPbI perovskite solar cells, it is highly important to realise a high open-circuit voltage. Calculation results based on a modified diode model have indicated that a low bare ratio ϕ of the perovskite film is the most important factor determining the open-circuit voltage, where ϕ is defined as the ratio of the projection of the uncovered area of the perovskite film to the apparent area of the total substrate surface. To realise a low ϕ, we investigate the nucleation behaviour of crystals on rough substrates. The analysis results predict that, when CHNHPbI is deposited on conventional transparent conductive oxide substrates such as fluorine-doped tin oxide, preferential heterogeneous nucleation will occur on the concave regions of the substrate; then, depending on the subsequent growth step, full coverage of the perovskite film at both the macroscopic and microscopic scales is realised. As a result, an ultra-high open-circuit voltage, i.e., 1.20 V, can be achieved in devices using the full coverage CHNHPbI film. The thermodynamics theory of precipitation nucleation should shed light on solution engineering of thin films.
为了获得高性能的 CHNHPbI 钙钛矿太阳能电池，实现高开路电压至关重要。基于改进的二极管模型的计算结果表明，钙钛矿薄膜的低裸露比ϕ是决定开路电压的最重要因素，其中ϕ定义为钙钛矿薄膜未覆盖区域的投影与总基底表面的表观面积之比。为了实现低ϕ，我们研究了晶体在粗糙基底上的成核行为。分析结果表明，当 CHNHPbI 沉积在传统的透明导电氧化物基底（如掺氟氧化锡）上时，会优先在基底的凹面发生异质成核；然后，根据后续的生长步骤，在宏观和微观尺度上都可以实现钙钛矿薄膜的完全覆盖。因此，在使用完全覆盖的 CHNHPbI 薄膜的器件中，可以实现超高压的开路电压，即 1.20V。沉淀成核的热力学理论应该为薄膜的溶液工程提供启示。
