Hole‐Transporting Materials for Perovskite‐Sensitized Solar Cells

Abstract

Organolead halide perovskites have attracted much interest from the scientific community in the past four years towards potential photovoltaic applications. A record efficiency of 20.1 % was reported in 2014. Some variation in efficiency is observed when the hole‐transporting material (HTM) used in perovskite solar cells (PSCs) is altered. This Review emphasizes the importance of HTMs as a means to elevate the already superior device performance to a new status. A basic introduction to perovskites as materials for photovoltaics is first provided. A plethora of HTMs used for the fabrication of these cells are then presented and the nuances of their chemistry are analyzed in detail. Finally, on the basis of the Review of HTMs, strategies that can be employed for synthesizing the “perfect” HTM for PSCs are discussed.

Functionalization of Graphene Oxide Films with Au and MoOx Nanoparticles as Efficient p‐Contact Electrodes for Inverted Planar Perovskite Solar Cells

“…Synthesis of Graphene Oxide : GO was synthesized using the Hummers method that was explained previously . For the preparation of HEL, GO solution (1 mg mL −1 in DMF) was spin‐coated on the ITO substrates (treated with UV‐O 3 for 20 min) at 4000 rpm for 40 s, followed by annealing at 125 °C for 10 min.…”

“…Various materials have been used as the hole‐extraction layer (HEL) or electron‐extraction layer in these device configurations . The inverted PHJ devices are particularly intriguing because charge separation would first occur at the p ‐contact HEL/perovskite interface that facilitates the transport of the hole carriers . A suitable HEL material for an inverted PHJ device should have the following characteristics: i) effective hole mobility, ii) a compatible energy level matching the valence‐band (VB) level of a perovskite, iii) excellent film formation from a solution‐based process, iv) great transparency in the visible and near infrared regions, and v) cost‐effective production of the material itself.…”

Low‐Cost Perovskite Solar Cells Employing Dimethoxydiphenylamine‐Substituted Bistricyclic Aromatic Enes as Hole Transport Materials

“…HTM is one of the key component as hole‐extracting layer facilitating hole transport toward the counter electrode, but also as electron‐blocking layer preventing back‐charge recombination . On the other hand, to ensure low‐cost perovskite solar cell manufacturing, an ideal HTM candidate has to be easily affordable by simple synthetic schemes with minimized number of steps and easy workup and purification procedures for cost‐effective upscale.…”

“…HTM is one of the key component as hole-extracting layer facilitating hole transport towardt he counter electrode, but also as electron-blocking layer preventing back-charge recombination. [7][8][9][10][11][12] On the other hand, to ensure low-cost perovskite solar cell manufacturing, an ideal HTM candidateh as to be easily affordable by simple synthetics chemes with minimized number of steps and easy workup and purification procedures for cost-effectiveu pscale. To date, molecular spiro-typeH TMs spiro-OMeTAD [2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene], [13,14] FDT {2',7'-bis[bis(4-methoxyphenyl)amino]spiro[cyclopenta(2,1-b:3,4-b')dithiophene-4,9'-fluorene]}, [15] and DDOF {2,2',7,7'-tetrakis-(N,N'-di-4-methoxyphenylamine)dispiro-[fluorene-9,4'-dithieno(3,2-c:2',3'-e)oxepine-6',9''fluorene]} [16] reached the highest reported values over 19 % along with variouso ther small-molecule HTMs based on paracyclophane, [17] truxene, [18] benzotrithiophene, [19,20] fluorene, [21,22] carbazole, [23][24][25] triazatruxene, [26,27] anthratetrathiophene, [28] phthalocyanine, [29,30] indoloindole, [31] and phenothiazine, [32] successfully reaching comparably high photovoltaic performance.…”

Anomalous Charge‐Extraction Behavior for Graphene‐Oxide (GO) and Reduced Graphene‐Oxide (rGO) Films as Efficient p‐Contact Layers for High‐Performance Perovskite Solar Cells

“…2018,8, 1701640 Photovoltaic parameters of inverted planar heterojunction perovskite solar cells fabricated with varied p-type HEL materials under simulated AM-1.5G illumination (power density 100 mW cm −2 ). Energy Mater.…”