Doping‐Free Asymmetrical Silicon Heterocontact Achieved by Integrating Conjugated Molecules for High Efficient Solar Cell

Abstract

Organic conjugated molecule/silicon (Si) heterojunction has been widely investigated to build up an asymmetrical heterocontact for efficient photovoltaics. However, it is still unclear how the organic molecular structures can affect their electronic coupling interaction with Si. Here, two widely explored electron acceptors of poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (N2200) and [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) are used to build up asymmetrical Si heterocontact to investigate their electronic coupling interaction. It is found that PCBM displays different electronic coupling with Si from N2200, which is ascribed to their various physical distance with Si based on a systematic and detailed density functional theory calculation. Organic layer incorporation not only suppresses the surface charge recombination velocity but also leads to an Ohmic contact between Si and Al. Therefore, a doping‐free organic/Si heterojunction photovoltaic with a power conversion efficiency of 14.9% is achieved with PCBM layer. This work discloses a key factor affecting organic/Si electronic coupling interaction, which helps build up high quality Si heterocontact for solar cells and other optoelectronic devices. Furthermore, the simplified heterocontact achieved by a low temperature, solution processed, and lithography‐free steps has a dramatic improvement on conventional diffusion doped‐silicon one at high temperature.

Over 16.7% Efficiency Organic‐Silicon Heterojunction Solar Cells with Solution‐Processed Dopant‐Free Contacts for Both Polarities

“…Furthermore, a large number of recombination centers exist at the unpassivated n‐Si/Al interface, causing photogenerated hole–electron pairs to be trapped and recombined readily. An effective approach to avoiding this Schottky barrier within the dopant‐free cell‐design regime is to insert a thin cathode interlayer, such as metal oxides, metal fluorides, or some organic materials . These cathode interlayers function as contact‐passivating layers by reducing the density of interfacial defects and alleviating Fermi‐level pinning, while providing sufficient conductivity of photogenerated electrons.…”

Photon management effects of hybrid nanostructures/microstructures for organic-silicon heterojunction solar cells

“…Besides, the PCBM layer can act as electron‐selective contacts as well as surface passivation layer. The details of PCBM effects can be found in the reference of Sun's work …”

“…Si wafers with different structured surfaces were cut into 1.5 cm × 1.5 cm square pieces to fabricate PEDOT:PSS/n-Si heterojunction solar cells. 41 Firstly, these samples were immersed into the dilute HF solution (volume ratio: HF/ H 2 O = 1:3) for 3 minutes to remove the native Si oxide and then cleaned by DI water and dried by N 2 . Subsequently, these samples were floated in a mixture of HF and HNO 3 (volume ratio: HF/HNO 3 = 1:20) for 5 minutes to polish the back structures.…”

Highly Conductive and Wettable PEDOT:PSS for Simple and Efficient Organic/c‐Si Planar Heterojunction Solar Cells

“…Although numerous works have confirmed modifying the PEDOT:PSS film capable of enhancing the efficiency for PEDOT:PSS/n‐Si heterojunction solar cells, it is not clear what the dominant origin for the improvement of conductivity of PEDPT:PSS film is . The working mechanism of the heterojunction and the relationship between the material properties of the PEDOT:PSS layer and the device performances are poorly understood, and it is not clear what the dominant origin for enhanced device performance based on the PEDOT:PSS interlayer is . The J SC and FF of PEDOT:PSS/n‐Si heterojunction solar cell are lower when compared with the conventional homogeneous p–n Si junction solar cell .…”