Heterojunction Engineering and Ideal Factor Optimization Toward Efficient MINP Perovskite Solar Cells

Abstract

The pursuit of high power conversion efficiency (PCE) and cost‐effective perovskite solar cells (PSCs) has spawned many innovative device structure designs. Compared with the traditional NIP type PSCs, electron transport layer (ETL) free PSCs have attracted growing attention due to their enormous potential in large area, low‐cost flexible application. However, there is still a lack of in‐depth understanding of the energy level arrangement indium tin oxide (ITO)/perovskite interface, resulting in poor device performance. Here, a metal/insulator/n‐type perovskite/p‐type spiro‐MeOTAD (MINP) structure is proposed to elaborate on the influence of the apparent work function and contact barrier change of the metal–semiconductor (MS) and metal–insulator–semiconductor (MIS) junction on the carrier transfer and collection. Common and easily available 5‐amino‐valeric acid is inserted into the ITO/perovskite interface to form an insulating dipole layer and to ensure quasi‐ohmic contact at the front interface. Consequently, the device changes from Schottky/PN cascade heterojunction type to a single PN heterojunction device with its ideal factor decreasing from 3.35 to 2.05. Accordingly, the champion device achieves 19.37% PCE with significantly increased Voc and FF compared to the pristine device. This work provides a facile and effective method to improve the application potential of novel ETL‐free PSCs.

In situ growth of a bifunctional modification material for highly efficient electron-transport-layer-free perovskite solar cells

“…The ultra-thin APS insulating layer could also effectively prevent electron recombination at the ITO/ PVK interface and transfer electrons through tunneling. 23 This was consistent with the photophysical test results that the APS modification could passivate defects and reduce energy loss at the interface.…”

“…35 The reason for the enhanced V oc is related to the low recombination of interfacial charges. 23 To explore the interfacial charge recombination in the devices, the relationship between V oc and light intensity was analyzed, as shown in Fig. 3f.…”

“…Inorganic monomolecular materials, including Cs 2 CO 3 , 17 hypophosphorous acid (H 3 PO 2 ), 18 tetramethylammonium (TMAH), 19 methylammonium acetate (MAAc), 20 and a-NbOH 8 could adjust the WF of the TCO and optimize the interfacial energy level alignment. Polyethylenimine ethoxylated (PEIE), 21 1-[ N -(2-hydroxyethyl)-4′-piperidyl]-3-(4′-piperidyl) propane (PPPDE), 22 and 5-amino-valeric acid (5-AVA) 23 were used as ultra-thin organic materials to form an interfacial dipole layer, which could mitigate the energy level mismatch.…”

Buried Interface Modification in Perovskite Solar Cells: A Materials Perspective

“…[130] Recently, taking advantage of these characteristics, Wang et al have utilized 5-AVA to form an oriented dipole layer on the indium tin oxide (ITO) surface to enhance the device performance of ETL-free PSCs. [131] It is worth noting that interface amino alone can also complete a good adjustment. [132] In addition, some amino acids can form an ambipolar self-assembled monolayer (SAM), which not only induces the growth of perovskite crystals but also improves the energy level alignment with an extra permanent dipole.…”

Interface compatibility: how to outperform classical spiro-OMeTAD in perovskite solar cells with carbazole derivatives

“…34 The stability of the unencapsulated PSCs FTO/SnO 2 /Cs 0.05 FA 0.85 MA 0.10 Pb(I 0.97 Br 0.03 ) 3 /spiro-OMeTAD/Ag and FTO/SnO 2 /Cs 0.05 FA 0.85 MA 0.10 Pb(I 0.97 Br 0.03 ) 3 /IL/HTM/Ag (where HTM is spiro-OMeTAD, Cz-Pyr or Cz-P ) were estimated by exposing the device to a relative humidity (of around 35%) in the atmosphere. 59,60 Fig. 3f shows the normalized PCE of the devices based on IL/spiro-OMeTAD, IL/ Cz-Pyr and IL/ Cz-P (values calculated out of 3 devices for each IL/HTMs composition) for an exposure time of 400 hours.…”