Molecular materials as interfacial layers and additives in perovskite solar cells

Solar cells based on organo-metal halide perovskites have gained unprecedented research interest over the last few years due to their low-cost solution processability, high power conversion efficiency, which has recently reached a certified value of 25.2%, and abundance of raw materials. Nevertheles...

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Bibliographic Details
Published in:Chemical Society reviews 2020-07, Vol.49 (13), p.4496-4526
Main Authors: Vasilopoulou, Maria, Fakharuddin, Azhar, Coutsolelos, Athanassios G, Falaras, Polycarpos, Argitis, Panagiotis, Yusoff, Abd. Rashid bin Mohd, Nazeeruddin, Mohammad Khaja
Format: Article
Language:English
Subjects:
Absorbers
Additives
Charge transfer
Charge transport
Commercialization
Crosslinking
Crystal defects
Current loss
Energy conversion efficiency
Energy levels
Interfacial energy
Metal halides
Morphology
Open circuit voltage
Optoelectronics
Perovskites
Photoelectric effect
Photoelectric emission
Photovoltaic cells
Radiative recombination
Raw materials
Solar cells
Structural stability
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Summary:Solar cells based on organo-metal halide perovskites have gained unprecedented research interest over the last few years due to their low-cost solution processability, high power conversion efficiency, which has recently reached a certified value of 25.2%, and abundance of raw materials. Nevertheless, the best efficiencies remain below the Shockley-Queisser theoretical limit of 32.5% due to several losses arising from either defect traps present in the bulk of the perovskite absorber or at the device heterointerfaces. While bulk defects are detrimental for the device performance by mainly limiting the open circuit voltage, interfacial layers are also crucial. They dictate the charge transfer/transport from the perovskite layer to the collecting electrodes, hence influencing the device photocurrent, but also act as protective barriers against oxygen and moisture penetration. Molecular materials and additives are widely used to improve the bulk properties of perovskite absorbers through the formation of high-quality perovskite films with superior optoelectronic properties, and improved crystallinity, and also of electronically clean interfaces with minimum losses during charge transfer/transport. In this review, we analyze the predominant pathways that contribute to voltage and current losses due to poor interfaces and also due to non-radiative recombination losses arising from inferior perovskite morphology and its inherent polycrystalline and highly defective nature. We then discuss strategies for achieving interfacial organic and inorganic molecular materials for application as electron and hole transport layers in perovskite solar cells with ideal energy levels, high charge mobilities and improved thermal, photo, and structural stability. Moreover, the prerequisites for molecular additives to achieve dimensionality engineering, defect passivation, molecular cross-linking, interfacial energy alignment and electronic doping are thoroughly discussed. Finally, we examine prospects for future research directions and commercialization. Here we review the recent strategies for developing organic and inorganic molecular materials for application as electron and hole transport layers and as additives to achieve high efficiency and stability perovskite solar cells.
ISSN:0306-0012
1460-4744
DOI:10.1039/c9cs00733d