Suppressing PEDOT:PSS Doping-Induced Interfacial Recombination Loss in Perovskite Solar Cells

Abstract

PEDOT:PSS is widely used as a hole transport layer (HTL) in perovskite solar cells (PSCs) due to its facile processability, industrial scalability, and commercialization potential. However, PSCs utilizing PEDOT:PSS suffer from strong recombination losses compared to other organic HTLs. This results in lower open-circuit voltage ( V OC ) and power conversion efficiency (PCE). Most studies focus on doping PEDOT:PSS to improve charge extraction, but it has been suggested that a high doping level can cause strong recombination losses. Herein, we systematically dedope PEDOT:PSS with aqueous NaOH, raising its Fermi level by up to 500 meV, and optimize its layer thickness in p-i-n devices. A significant reduction of recombination losses at the dedoped PEDOT:PSS/perovskite interface is evidenced by a longer photoluminescence lifetime and higher magnitude of surface photovoltage, leading to an increased device V OC , fill factor, and PCE. These results provide insights into the relationship between doping level of HTLs and interfacial charge carrier recombination losses.

PEDOT:PSS/CuCl Composite Hole Transporting Layer for Enhancing the Performance of 2D Ruddlesden–Popper Perovskite Solar Cells

“…Therefore, a more comparable wettability of the PEDOT:PSS/CC-2 film with DMF is beneficial for transforming 2D perovskite precursors into the desirable 2D perovskite crystal phase, further enabling the formation of high-coverage uniform films. Moreover, combined with the fact that the added NH 3 ·H 2 O cannot affect the nucleation process or growth rate of the BA 2 MA 3 Pb 4 I 13 crystal, this surface optimization could be attributed to the existence of chloride, which can delay the crystallization and enhance the crystal quality of films, as demonstrated in previous reports. ,, …”

“…Nevertheless, PEDOT:PSS shows some shortcomings. For instance, its work function (−5.1 eV) does not match with the valence band of the 2D RP perovskite layer (−5.4 eV). , In particular, the hygroscopic and acidic nature of PSS often contributes to some instability issues, such as oxidation of some metals or metal oxides, and detriment of some active materials with basic characteristics in 2D RP PSCs. − These problems greatly offset the benefit of using stable 2D RP perovskites as light absorbers. , Consequently, modifying PEDOT:PSS becomes an effective way to overcome these weaknesses but maintain the original advantages of PEDOT:PSS for fulfilling highly efficient and stable 2D RP PSCs. , …”

Recent advances in the interfacial engineering of organic–inorganic hybrid perovskite solar cells: a materials perspective

“…Recently, to address the problem of recombination loss due to doping of PEDOT:PSS, aqueous NaOH was used to de-dope the PEDOT:PSS layer and to increase the conductivity by adjusting the thickness of the layer to achieve effective charge transport. 156 The de-doped PEDOT:PSS/perovskite interface demonstrated a significantly lower recombination loss, leading to an increase in the device V oc , FF and PCE. This modification strategy provided a potential direction for the application of PEDOT:PSS in inverted PSCs.…”

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

“…However, the J SC hysteresis characteristic in the J-V curves can still be observed, which means the existence of halide vacancies inside the crystalline grains (point defects) in the bottom region of the perovskite thin film. Conceptually, the hydrogen cations in the sulfonic acid (-SO 3 H) groups can be substituted by the sodium cations with the addition of NaOH into the PEDOT:PSS/water solution [ 38 ], which results in the stable PSS polymers. In other words, the use of a stable PEDOT:PSS thin film with the dehydrogenation reaction can reduce the formation of halide vacancies in the perovskite crystalline thin film, which might improve the photovoltaic performance of the inverted perovskite solar cells.…”

“…Poly(triarylamine) (PTAA)- and poly[3-(4-carboxybutyl) thiophene-2,5-diyl] (P3CT)-based thin films have been widely used to replace the PEDOT:PSS thin films, which can increase the V OC and FF of the resultant perovskite solar cells simultaneously [ 31 , 32 , 33 , 34 ]. It can be explained as being due to the reductions of potential loss and carrier recombination in the perovskite layer and at the perovskite/HTL interface [ 35 , 36 , 37 , 38 ]. The surface wettabilities of the PEDOT:PSS, P3CT-X (X: Na, K, Rb, Cs) and PTAA thin films are super-hydrophilic, hydrophilic and hydrophobic, respectively, which can largely influence the film discontinuity and grain size of the deposited perovskite thin films [ 39 , 40 ].…”