Homojunction perovskite solar cells: opportunities and challenges

Abstract

Organometallic halide perovskites have rapidly become promising materials as a result of their outstanding properties in high-efficiency and low-cost next-generation solar cells. Perovskite materials can be adjusted to be p- or n-type by defect engineering through, for example, the self-doping method by controlling the precursor compositions and process conditions. Recently, a p-type perovskite/n-type perovskite homojunction has been proposed and constructed, which provides a possibility for the design of a novel type of perovskite solar cell (PSC). Following a brief overview of the physical fundamentals of perovskite homojunctions, a detailed discussion of the promising progress of recently reported homojunction PSCs is presented here, including theoretical simulations, extrinsic and interfacial doping and graded structures. Furthermore, the opportunities regarding higher doping concentrations, simpler device architectures, ion migration inhibition and device stability are discussed. Finally, an outlook that offers insights into the future development of highly efficient and stable homojunction PSCs is provided.

Recent progress of crystal orientation engineering in halide perovskite photovoltaics

“…The presence of structural disorder caused by crystallinity, crystallographic orientation and defects in a crystal should be responsible for different charge-carrier transport properties. 79,80 Considering the crystal anisotropy of the tetragonal MAPbI 3 structure, anisotropic carrier transport of MAPbI 3 has been widely investigated to understand its effect on device performance, and it is reasonable to expect that the highly ordered lattice packing could reduce disordered electronic states and improve the charge transport properties. 81 Anisotropic optoelectronic performances were reported in the case of MAPbI 3 single crystals with the natural exposed ( 100) and (112) facets; 135% increased responsivity and 128% enhanced EQE were observed on the photo-detectors based on the (112) plane and the (100) plane, respectivly.…”

Chitosan Derivatives Modified with SnO2 for High-Efficiency Carbon-Based Perovskite Solar Cells

“…Therefore, the C-PSCs have larger built-in potential, 34 smaller potential barrier for charge transfer from the perovskite layer to the SnO 2 ETL, less charge accumulation at the interface, and longer charge lifetime, thus suppressing the charge recombination. 35 As a result, the addition of HACC and CMCS increased the PCE of the C-PSCs from 10.17 to 12.42 and 13.39%, which were increased by 22.12 and 31.66% compared with the control device. Moreover, after being stored in an air environment for 30 days, the unencapsulated optimal H−SnO 2 and C−SnO 2 ETL-based C-PSCs maintained 92.3 and 96.5% of the initial PCE, respectively, while the pure SnO 2 -based C-PSCs only maintained 81%, which demonstrates that the addition of HACC and CMCS also greatly improved the long-term stability of C-PSCs.…”

“…Because of the interaction with terminal active functional groups, the addition of HACC and CMCS not only improved the dispersion and crystallinity of SnO 2 and CH 3 NH 3 PbI 3 but also passivated the oxygen vacancy defects on the surface and improved the conductivity. Therefore, the C-PSCs have larger built-in potential, smaller potential barrier for charge transfer from the perovskite layer to the SnO 2 ETL, less charge accumulation at the interface, and longer charge lifetime, thus suppressing the charge recombination . As a result, the addition of HACC and CMCS increased the PCE of the C-PSCs from 10.17 to 12.42 and 13.39%, which were increased by 22.12 and 31.66% compared with the control device.…”

Regulating the crystallization dynamics through hydrogen bonding for high efficiency tin halide perovskite solar cells

“…As one of the most promising lead-free analogues, tin halide perovskite solar cells (TPSCs) have obtained massive research interest and achieved a record PCE of 14.81%, 1 but mainly suffered from fast crystallization, 2,3 high open-circuit voltage (V oc ) deficit, 4 and easy oxidation. 5 It has been well recognized that the film quality of the perovskite layer is a critical factor determining the PCE of TPSCs.…”