Inverted organic solar cells with non-clustering bathocuproine (BCP) cathode interlayers obtained by fullerene doping

Abstract

Bathocuproine (BCP) is a well-studied cathode interlayer in organic photovoltaic (OPV) devices, where it for standard device configurations has demonstrated improved electron extraction as well as exciton blocking properties, leading to high device efficiencies. For inverted devices, however, BCP interlayers has shown to lead to device failure, mainly due to the clustering of BCP molecules on indium tin oxide (ITO) surfaces, which is a significant problem during scale-up of the OPV devices. In this work, we introduce C 70 doped BCP thin films as cathode interlayers in inverted OPV devices. We demonstrate that the interlayer forms smooth films on ITO surfaces, resulting from the introduction of C 70 molecules into the BCP film, and that these films possess both improved electron extraction as well exciton blocking properties, as evidenced by electron-only devices and photoluminescence studies, respectively. Importantly, the improved cathode interlayers leads to well-functioning large area (100 mm 2 ) devices, showing a device yield of 100%. This is in strong contrast to inverted devices based on pure BCP layers. These results are founded by the effective suppression of BCP clustering from C 70 , along with the electron transport and exciton blocking properties of the two materials, which thus presents a route for its integration as an interlayer material towards up-scaled inverted OPV devices.

High voltage vacuum-processed perovskite solar cells with organic semiconducting interlayers

“…25 This widely accepted view is challenged by recent reports where BCP was found to efficiently mediate electron transfer when placed in between an indium tin oxide (ITO) electrode and C 60 , where the formation of organometallic species is unlikely. 29 In perovskite solar cells, non-radiative recombination is dominant at dislocations, grain boundaries, impurities as well as at the contact interface, and in all cases it unavoidably diminishes the attainable open-circuit voltage. 30 Non-radiative recombination in the perovskite layer can be regulated through controlled lm crystallization/ processing, while interface recombination should be minimized through the choice of suitable transport materials and optimized device architectures.…”

Enhanced thermal stability of inverted perovskite solar cells by interface modification and additive strategy

“…1e and f. The BCP lm aer 12 h of heating under 85 C has exhibited a high level of clustering and aggregation 24 which is clearly attributed to thermal heating. Differential Scanning Calorimetry (DSC) thermograph of BCP powder is shown in Fig.…”

“…The appearance of BCP molecule clustering has resulted the root-mean-square roughness of the lm increasing from 6.68 nm before thermal aging to 10.42 nm aer thermal aging. The increased BCP lm roughness can potentially lead to a certain degree of electrical shunting 24 of the device that consequently hampers the device performance.…”

Understanding the PEDOT:PSS, PTAA and P3CT-X Hole-Transport-Layer-Based Inverted Perovskite Solar Cells

“…In the regular perovskite solar cell, the use of a hole modification layer can increase the hole collection efficiency and block the photogenerated electrons from the perovskite layer [ 101 , 102 , 103 ]. In the inverted perovskite solar cells, the film quality of the ETL and the contact quality at the ETL/perovskite interface can be improved via a BCP/IPA solution treatment process, which can improve V OC , J SC and FF simultaneously [ 104 , 105 , 106 ]. Au (Cu) and Ag (Al) metals are used as the anode electrode and cathode electrode, respectively.…”