Solution‐Processable Ultrathin Black Phosphorus as an Effective Electron Transport Layer in Organic Photovoltaics

Abstract

2D van der Waals crystals, possessing excellent electronic and physical properties, have been intriguing building blocks for organic optoelectronic devices. Most of the 2D materials are served as hole transport layers in organic devices. Here,it is reported that solution exfoliated few layers black phosphorus (BP) can be served as an effective electron transport layer (ETL) in organic photovoltaics (OPVs) for the first time. The power conversion efficiencies (PCEs) of the BP‐incorporated OPVs can be improved to 8.18% in average with the relative enhancement of 11%. The incorporation of BP flakes with the optimum thickness of ≈10 nm can form cascaded band structure in OPVs, which can facilitate electron transport and enhance the PCEs of the devices. This study opens an avenue in using solution exfoliated BP as a highly efficient ETL for organic optoelectronics.

Black Phosphorus Rediscovered: From Bulk Material to Monolayers

“…[253] Reprinted from Refs. To the best of our knowledge,o nly top-down methods have been reported for the synthesis of few-and single-layer BP.…”

“…Besides the above applications,BPhas also been tested as anew material for water splitting, [73,[247][248][249][250][251] photovoltaic (PV) solar cells, [214,252,253] and photodetectors. [86,203,[224][225][226][227][228][229][230] Wang and co-workers developed athermal-vaporization transformation (TVT) to deposit orthorhombic BP on athin Ti foil and CNT matrix to obtain BP thin films and BP particles for anodic water splitting.…”

“…[258] Graphene has azero band gap and TMDs, specifically MoS 2 ,h as an indirect band-gap energy of 1.23-1.69 eV,b ut semiconductor BP has at unable band gap with ap redicted direct band gap of 0.3-2.0 eV, [55,59,126,[259][260][261][262][263][264][265] which suggests the suitability of BP for solar water splitting. [214,252,253] Ultrasmall BP QDs incorporated into ap olyaniline (PANI) film can function as an absorber of NIR light and charge-transfer layer in the photocathode of ab ifacial n-type dye-sensitized solar cell ( Figure 6C). [214,252,253] Ultrasmall BP QDs incorporated into ap olyaniline (PANI) film can function as an absorber of NIR light and charge-transfer layer in the photocathode of ab ifacial n-type dye-sensitized solar cell ( Figure 6C).…”

“…Theb roadband absorption of light leads to al ight-to-electron power conversion efficiency( PCE) of about 7%,a ne nhancement of about 20 %w ith respect to an electrode without BP QDs, because of the fast carrier transfer and complementary light absorption by the BP QDs. [253] Ad etailed review of the potential applications of BP in solar cells has recently been published. ThePCE of the BP-incorporated OPV cell can be 11 %, with al ight-to-electron PCE of about 8% ( Figure 6D).…”

Black Phosphorus: Synthesis and Application for Solar Cells

“…The reduced performance was associated with the fact that the mismatched energy alignment of the BP layer in the device potentially trapped the holes and blocked the hole-transporting Adv. [50] Copyright 2016, WILEY-VCH. 2018, 8, 1701832 Figure 2.…”