Optimization of In-situ and Ex-situ doped p+ Passivating Contact for High Efficiency p-TOPCon Solar Cell Application

Wook Jin Choi, Keeya Madani, Ying Yuan Huang, Aditi Jain, Young Woo Ok, Vijaykumar D. Upadhyaya Min Gu Kang, Sungjin Choi, Ajeet Rohatgi

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Scopus citations


This paper presents fabrication and optimization of p+ passivating contact (p+ poly-Si/SiOx/c-Si) for high efficiency p-TOPCon solar cells. The p+ passivating contacts were formed by (i) in-situ doped p+ poly-Si via LPCVD and (ii) ex-situ doping of intrinsic poly-Si via APCVD boron diffusion. We studied the relationship between the passivation quality of this contact as a function of boron diffusion profile varied by altering (i) the crystallization annealing temperature, and (ii) the APCVD precursor gas flow ratio \left( {{\emptyset _{{B_2}{H_6}}}/{\emptyset _{Si{H_4}}}} \right). In-situ doping resulted in higher B concentration in poly-Si, which improves field induced passivation, as well as in Si absorber near the interface, which enhances Auger recombination to degrade passivation. This trade-off resulted in lower optimum annealing temperature for in-situ process (875°C vs 950°C). However, process optimization resulted in excellent passivation with comparable iVoc and J0 for both in-situ (719mV/6.3fAcm-2) and ex-situ doped (716mV/6.6fAcm-2) un-metallized p-TOPCon. Greater than 22.0% screen-printed large area (244.32cm2) bifacial p-TOPCon solar cells were fabricated by replacing LBSF of p-PERC cells with 270 nm p+ TOPCon junction with 10% metal coverage on the rear side. TOPCon cells gave 0.4% higher efficiency than their PERC counterpart.

Original languageEnglish
Title of host publication2021 IEEE 48th Photovoltaic Specialists Conference, PVSC 2021
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages6
ISBN (Electronic)9781665419222
StatePublished - 20 Jun 2021
Event48th IEEE Photovoltaic Specialists Conference, PVSC 2021 - Fort Lauderdale, United States
Duration: 20 Jun 202125 Jun 2021

Publication series

NameConference Record of the IEEE Photovoltaic Specialists Conference
ISSN (Print)0160-8371


Conference48th IEEE Photovoltaic Specialists Conference, PVSC 2021
Country/TerritoryUnited States
CityFort Lauderdale


  • ex-situ doping
  • hole selective contact
  • in-situ doping
  • p-TOPCon
  • passivating contact
  • poly-Si


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