Effective on January 1, 2018, the Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers (Topic 606). The standard establishes the principles that an entity shall apply to report useful information to users of financial statements about the nature, amount, timing, and uncertainty of revenue and cash flows from a contract with a customer.

During the year ended December 31, 2019, the Company entered into a transaction with one of its customers for emitters involving elements of variable consideration. Due to the escalation in trade policy tension between the governments of China and the United States, the customer required a larger than normal shipment of emitters having a right to return them through March 15, 2020 in order to accommodate their uncertain production needs. Per Topic 606, the Company was constrained to recognizing revenue on this unique shipment to the extent that it was probable that a significant revenue reversal would not occur and deferred recognition of the remainder until after the inherent uncertainties of the transaction were resolved. These uncertainties included factors that were outside of the Company’s influence, including the customer’s production needs and complexities associated with the current international health and trade issues in China. On March 15, 2020, the inherent uncertainties of the transaction were resolved as the customer did not exercise their right of return provision. This event resulted in the recognition of the previously constrained revenue during the three months ended March 31, 2020.

For the three months ended March 31, 2020 and 2019, the Company recorded 98% and 97% of its revenue from sales of materials, respectively, and 2% and 3% from the providing of services through Adesis, respectively.

The following table provides information about assets and liabilities associated with our contracts from customers (in thousands):

	As of March 31, 2020
Accounts receivable	$	82,592
Short-term unbilled receivables		2,757
Short-term deferred revenue		99,565
Long-term deferred revenue		49,866

Short-term and long-term unbilled receivables are classified as other current assets and other assets, respectively, on the Consolidated Balance Sheets. The deferred revenue balance at March 31, 2020 will be recognized as materials are shipped to customers over the remaining contract periods. The significant customer contracts (individually representing greater than 10% of revenue) expire in 2022. As of March 31, 2020, the Company had $5.2 million of backlog associated with committed purchase orders from its customers for phosphorescent emitter material. These orders are anticipated to be fulfilled within the next 90 days.

Significant changes in the unbilled receivables and deferred liabilities balances for the three months ended March 31, 2020 and 2019, are as follows (in thousands):

	Three Months Ended March 31, 2020
	Unbilled Receivables Increase (Decrease)		Deferred Revenue (Increase) Decrease
Balance at December 31, 2019	$	1,362	$	(144,862	)
Revenue recognized that was previously included in deferred revenue		—		38,749
Increases due to cash received		—		(43,685	)
Cumulative catch-up adjustment arising from changes in estimates of transaction price		—		367
Unbilled receivables recognized		1,395		—
Transferred to receivables from unbilled receivables		—		—
Net change		1,395		(4,569	)
Balance at March 31, 2020	$	2,757	$	(149,431	)

	Three Months Ended March 31, 2019
	Unbilled Receivables Increase (Decrease)			Deferred Revenue (Increase) Decrease
Balance at December 31, 2018	$	1,020		$	(122,567	)
Revenue recognized that was previously included in deferred revenue		—			27,596
Increases due to cash received		—			(33,080	)
Cumulative catch-up adjustment arising from changes in estimates of transaction price		—			159
Transferred to receivables from unbilled receivables		(779	)		—
Net change		(779	)		(5,325	)
Balance at March 31, 2019	$	241		$	(127,892	)