SUMMARY OF PRINCIPAL ACCOUNTING POLICIES - Restricted cash (Details) - USD ($) |
Dec. 31, 2022 |
Dec. 31, 2021 |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|---|---|
| SUMMARY OF PRINCIPAL ACCOUNTING POLICIES | ||||
| Cash and cash equivalents | $ 107,104,714 | $ 254,065,589 | ||
| Restricted cash | 182,544 | 316,777 | ||
| Total cash, cash equivalents, and restricted cash | $ 107,287,258 | $ 254,382,366 | $ 40,676,311 | $ 24,697,153 |