Lithography-free and dopant-free back-contact silicon heterojunction solar cells with solution-processed TiO2 as the efficient electron selective layer

Zhou

et al. 2021

Adv Funct Materials

As one of the most promising photovoltaic materials, the efficiency of inorganic-organic hybrid halide perovskite solar cells (PSCs) has reached 25.5% in 2020. However, the stability and hysteresis remain primary challenges before it can become a commercial photovoltaic technology. Therefore, those issues have drawn significant attention for photovoltaic applications. In this work, a study of the PSCs hysteresis improvement is presented based on a combination of first-principles simulations, scanning electron microscopy images, and time-dependent photocurrent measurements. It indicates the hysteresis led by the ion migration and accumulation is mainly localized at the two interfaces: one is between electron transport layer and active layer, and the other is between active layer and hole transport layer. Considering the massive defects at the grain boundaries (GBs), they lower the potential barriers significantly. The defect density at GBs is therefore reduced via the in situ passivation of PbI 2 crystals. The hysteresis index is decreased from 22.43% down to 1.04%, and results in an improvement in efficiency from 17.12% up to 20.10%. Following the understanding of defect-induced hysteresis, an approach to improve the hysteresis is provided, which can be integrated into the fabrication process and widely applied to enhance the performance of PSCs.

Section: Introductionmentioning

confidence: 93%

In Situ Management of Ions Migration to Control Hysteresis Effect for Planar Heterojunction Perovskite Solar Cells

Zhou

et al. 2021

Adv Funct Materials

“…Recently, a remarkable efficiency of 23.5% was reached for silicon heterojunction solar cells using hole-collecting and transparent MoO x (4 nm) to replace a-Si:H(p) . Additionally, wide variety of electron selective contact materials, such as metals (e.g., Ca, Mg, , Sc, and Yb), metal oxides (e.g., MgO, TiO 2 , , ZnO, Ta 2 O x , BaO x , and Nb 2 O 5 ), metal nitrides (e.g., TaN x , TiN x ), fluoride salts (e.g., LiF x , and MgF 2 ), carbonates (e.g., CsCO 3 , K 2 C x O y , Rb 2 C x O y , CaC x O y , SrC x O y , and BaC x O y ), , and their stack combination, ,, have been successfully inserted between metal and n-Si to reduce the Schottky barrier and eliminate the Fermi level pinning effect at the Al/n-Si interface. Moreover, full dopant-free silicon solar cell technologies utilizing dopant-free hole and electron transport layers simultaneously have the potential to be a highly efficient and low-cost technique in the field of industrial silicon solar cells. , …”

Section: Introductionmentioning

confidence: 99%

Degradation Mechanism and Stability Improvement of Dopant-Free ZnO/LiF_x/Al Electron Nanocontacts in Silicon Heterojunction Solar Cells

Lin

Boccard

Zhong

et al. 2020

ACS Appl. Nano Mater.

Dopant-free passivating contacts for photovoltaics have the potential to be deposited at low costs while providing excellent surface passivation and low contact resistance. However, one pressing issue of dopant-free carrier selective contacts is their lower environmental stability compared to conventional silicon-based contacts. In this contribution, we study the degradation in the ZnO/LiF x /Al electron selective nanocontact with experiments and simulations and suggest design modifications for higher performance and stability. Using a thicker metallization and optimal ZnO deposition temperature (130 °C), we improved open-circuit voltage and fill factor, together with improved stability with retention of over 93 and 88% of the initial open-circuit voltage and fill factor after storage in air for 380 h. The champion device has reached an efficiency of 21.3% with V OC of 727 mV, J SC of 37.6 mA/cm2, and FF of 78.0%. Furthermore, the enhanced stability in vacuum, scanning transmission electron microscopy (STEM) images, and the current-exchange simulation suggests that the degradation of the a-Si:H(i)/ZnO/LiF x /Al contact is caused by a drop of the LiF x /Al work function, due to interaction with air. This work has developed a deep understanding of the degradation mechanism and the methodology of stability analysis for dopant-free silicon solar cells.

2020 47th IEEE Photovoltaic Specialists Conference (PVSC)

“…29,30 Those materials are similarly attractive in SHJ solar cells for their ability to induce an efficient carrier selectivity for both hole and electron transport layers. [31][32][33][34][35][36][37][38] When TMO films replace the highly doped silicon-based layers on the illuminated side of the device, parasitical absorption losses can be strongly mitigated, resulting in clear current gain. 31,33,34,39,40 Among TMOs, molybdenum oxide (MoO x ) is promising for applications as hole transport layer (HTL) in replacement of the traditionally used (p)a-Si:H in SHJ device.…”

Section: Introductionmentioning

confidence: 99%

Strategy to mitigate the dipole interfacial states in (i)a-Si:H/MoO_xpassivating contacts solar cells

Mazzarella

Alcaniz-Moya

Kawa

et al. 2020